1. Field of the Invention
The invention relates generally to the manufacture of encapsulated electric coils for use in electromagnetic devices. More particularly, the invention relates to a device for positioning and supporting such a coil within a mold for encapsulation by a dielectric material.
2. Summary of Related Art
Encapsulated coils are well known devices used in a wide variety of applications. Such encapsulated coils are formed of a coil of metal wire which is disposed within a metal shell and encapsulated with a dielectric material. An insulating ring, also formed of a dielectric material, is secured between the coil and the shell to prevent any electrical connection therebetween.
To form such an encapsulated coil, the metal shell is placed in a lower mold portion, and the insulating ring is positioned within the shell. A typical insulating ring is formed of a substantially flat ring having a pair of tabs extending perpendicularly from the outer circumference thereof. The coil is then positioned on top of the insulating ring and is spaced apart from the tabs. An upper mold portion is placed on the lower mold portion. This upper mold portion includes a core which extends within a central passage of the coil.
Means are generally provided for positioning the coil relative to the mold. Typically, the upper mold portion includes a number of fingers which engage the inner periphery of the coil to position the coil properly relative to the mold. The outer periphery of the coil is spaced radially inwardly a uniform distance from the peripheral wall of the mold, and the inner periphery of the coil is spaced radially outwardly a uniform distance from the peripheral wall of the mold core. The exposed surfaces of the coil and the insulating ring are encapsulated by the moldable, dielectric material. However, those portions of the coil which are in contact with the positioning fingers are not encapsulated.
Thus, with the positioning fingers used previously, portions of the coil wire remain exposed in the completed coil assembly. It would therefore be desirable to provide a locating ring which properly positions the coil within the mold and allows the complete encapsulation thereof, while also insulating the coil from the metal shell.
Furthermore, the cycle times for the injection molding systems typically used in the manufacture of electric coils have increasingly become shorter. The faster injection of the moldable dielectric material has made it more difficult to allow for proper venting of the mold. This, in turn, has resulted in a greater number of bubbles and defects in the post-molded coil assembly. It would therefore also be advantageous to provide an improved locating ring which permits faster injection of the dielectric material.